Nanocapsules and uses thereof

Abstract

The present disclosure concerns use of a nanocapsule for thermal regulation of hair, scalp, and / or skin, comprising a step of contacting the nanocapsule with the hair, scalp, and / or skin; wherein the nanocapsule comprises a shell and a core; wherein the core comprises a phase change material configured to absorb heat from the hair, scalp, skin and / or an environment adjacent to the hair, scalp, and / or skin. The present disclosure also concerns a method of cooling hair, scalp and / or skin.

Description

[0001] Nanocapsules and Uses Thereof

[0002] Technical Field

[0003] The present invention relates, in general terms, to nanocapsules and their uses thereof.

[0004] Background

[0005] Current hair cooling products in the market work by using menthol or its derivatives e.g. tea tree, eucalyptus, peppermint. These chemicals work by activating the TRPM8 receptor, causing an influx of Ca2+into sensory nerve cells, and thereby giving the user a tingling / refreshing sensation. However, the effects are very short-lived. Once the product is washed away and no longer in contact with the skin, the cooling feeling will disappear within seconds. This is not ideal as it is only when consumers are out of the shower, that they need the cooling effect even more. Furthermore, menthol and its derivatives may cause skin sensitivity, dry skin, allergic reactions, dryness and irritation to the skin and eyes.

[0006] Thus, there is a need to develop an alternative product for menthol hair products which stays on the hair and buffers the temperature of the hair, scalp, and / or skin by a few degrees throughout the day, thereby providing long-lasting cooling effects for the user.

[0007] It would be desirable to overcome or ameliorate at least one of the above-described problems, or at least to provide a useful alternative.

[0008] Summary

[0009] The present disclosure concerns use of a nanocapsule for thermal regulation of hair, scalp, and / or skin, comprising a step of contacting the nanocapsule with the hair, scalp, and / or skin;

[0010] wherein the nanocapsule comprises a shell and a core;

[0011] wherein the core comprises a phase change material configured to absorb heat from the hair, scalp, skin and / or an environment adjacent to the hair, scalp, and / or skin.

[0012] In some embodiments, the phase change material comprises at least two fatty acids.

[0013] In some embodiments, the phase change material is a lipophilic material.In some embodiments, the at least two fatty acids are independently selected from Cs to C20 fatty acids. In some embodiments, the at least two fatty acids are independently selected from Cs to Cis fatty acids.

[0014] In some embodiments, the at least two fatty acids are saturated fatty acids.

[0015] In some embodiments, the at least two fatty acids are selected from caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and a combination thereof.

[0016] In some embodiments, the phase change material is characterised by a melting range of about 15 °C to about 40 °C. In some embodiments, the melting range is about 30 °C to about 35 °C.

[0017] In some embodiments, the phase change material is characterised by a solidification temperature range of about 15 °C to about 40 °C.

[0018] In some embodiments, the core is characterised by a size of about 10 nm to about 1000 nm.

[0019] In some embodiments, the shell is a polymer shell and / or a silica shell.

[0020] In some embodiments, the shell is characterised by a thickness of about 1 nm to about 200 nm. In some embodiments, the thickness is about 20 nm to about 100 nm. In some embodiments, the thickness is about 1 nm to about 30 nm.

[0021] In some embodiments, the shell is non-porous.

[0022] In some embodiments, the phase change material is not releasable from the nanocapsule.

[0023] In some embodiments, the nanocapsule is characterised by a particle size of about 70 nm to about 1500 nm.

[0024] In some embodiments, the nanocapsule is characterised by a temperature decrease of about 2.5 °C to about 5 °C when the phase change material melts.In some embodiments, the phase change material is characterised by a melting duration of about 1 minute to about 100 minutes.

[0025] In some embodiments, the nanocapsule is configured to withstand at least two heatmelt cycles without leaching of the phase change material.

[0026] In some embodiments, the nanocapsule is configured to not leach the phase change material at a temperature range of about 15 °C to about 40 °C.

[0027] In some embodiments, the nanocapsule is characterised by a thermal conductivity of about 0.1 W / rri'K to about 0.3 W / ni'K.

[0028] In some embodiments, the nanocapsule is characterised by a latent heat of fusion of about 150 kJ / kg to about 250 kJ / kg.

[0029] The present disclosure also concerns a method of cooling hair, scalp, and / or skin, comprising applying a formulation to hair, scalp, and / or skin;

[0030] wherein the formulation comprises nanocapsules as disclosed herein.

[0031] In some embodiments, the formulation comprises nanocapsules at a wt% of about 0.1 wt% to about 5 wt% relative to the formulation.

[0032] The present disclosure also concerns a nanocapsule as disclosed herein.

[0033] The present disclosure also concerns a formulation, comprising nanocapsules as disclosed herein.

[0034] Brief description of the drawings

[0035] Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the drawings in which:

[0036] Figure 1 shows an embodiment of the nanocapsule.

[0037] Figure 2 shows the temperature change of two embodiments of the nanocapsule against two negative controls.

[0038] Figure 3 shows some advantages of the nanocapsule. Temp refers to temperature.

[0039] Figure 4 shows the designed temperature response of the nanocapsule in response tothe external temperature. "Design Temp" refers to the designed melting temperature of the nanocapsule.

[0040] Figure 5 shows an experimental setup for studying the cooling effect of two embodiments of the nanocapsule.

[0041] Figure 6 shows a schematic diagram of the experimental setup of Figure 5.

[0042] Figure 7 shows the cooling effect of two embodiments of the nanocapsule.

[0043] Detailed description

[0044] The present disclosure concerns a nanocapsule comprising a phase change material (PCM) to provide cooling effect, such as hair cooling, scalp cooling and / or skin cooling and its use thereof. PCMs may absorb and release large amounts of thermal energy during phase change process, allowing for storage and release of thermal energy which may be used for cooling applications. PCMs may also be used for passive cooling, where phase change may occur without the need for an active cooling system such as a refrigerator or an air conditioner. Different PCMs may undergo phase change at different temperatures, allowing for use at different temperatures as desired. The nanocapsule may be mixed with hair care products to be applied onto hair, scalp, and / or skin for cooling applications.

[0045] The thermal energy may be absorbed from the environment, such as from the hair, scalp, skin and / or an environment adjacent to the hair, scalp and / or skin. This absorption of thermal energy may help to combat heat associated conditions arising from global warming. PCMs may absorb excess heat from the hair, scalp, skin and / or the environment adjacent to the hair, scalp and / or skin. This may help to regulate the temperature and prevent heat buildup and may provide a cooling effect that may alleviate heat-related discomfort and stress. By absorbing heat from the environment, PCMs may help to mitigate the impact of elevated ambient temperatures associated with global warming and may help reduce heat-related illnesses such as heat exhaustion, heat stroke and dehydration, due to the cooling effect provided by PCMs.

[0046] Accordingly, the present disclosure concerns use of a nanocapsule forthermal regulation of hair, scalp, and / or skin, comprising a step of contacting the nanocapsule with the hair, scalp, and / or skin;

[0047] wherein the nanocapsule comprises a shell and a core;

[0048] wherein the core comprises a phase change material configured to absorb heat from the hair, scalp, skin and / or an environment adjacent to the hair, scalp, and / or skin.The nanocapsule, and its formulation thereof, may thus be applied onto an external surface of a human body or mammal. The nanocapsules may be incorporated into various personal care product formulations, such as shampoos, conditioners, skin care products and cosmetics. The use of biocompatible materials, such as a polymer and / or silica shell, and encapsulation of the phase change material may help to ensure the safety and acceptability of the nanocapsule for topical application onto a human body or mammal.

[0049] A nanocapsule is a type of nanoparticle that may comprise a core material encapsulated within a shell. The core may form the inner part of the nanocapsule and may comprise an active or functional material. The core may be a solid or a liquid, such as oils, paraffin wax or fatty acids. The shell may be the outer layer that surrounds and encapsulates the core and is selected to provide specific properties such as protection of the core. The shell may completely enclose and encapsulate the core, forming a protective barrier around it, and isolating the core from the external environment, preventing unwanted interactions or degradation. The shell may be made of polymers, silica or other inorganic materials.

[0050] According to Figure 1, the core is the inner part of the nanocapsule, which may comprise the active or functional material. The core comprises a phase change material. The core may be a solid or a liquid. The shell is the outer layer that surrounds and encapsulates the core. The shell material may protect the core material by isolating the core from the external environment, and may prevent leakage, oxidation, evaporation and / or degradation. This may help to maintain the integrity and stability of the phase change material during thermal cycling. The PCM absorbs heat conductively via the shell.

[0051] A PCM is a substance which releases or absorbs energy at phase transition or phase change. The energy may be thermal energy. Phase change may be from solid to liquid, liquid to solid, liquid to gas, gas to liquid, or from one crystalline structure to another crystalline structure of higher or lower energy state within a temperature range. When the surrounding temperature exceeds the phase change temperature of the PCM, the PCM may start to absorb heat. As the PCM absorbs heat, it may undergo a phase change from a solid to a liquid state. The process may require a large amount of energy to be absorbed by the PCM, thus cooling the surrounding environment. The PCM may store the thermal energy as latent heat, which may be subsequently released when the surrounding temperature drops below the phase change temperature of the PCM. Asthe temperature decreases, the PCM may undergo a reverse phase change from liquid to solid, releasing the stored latent heat and heating the surrounding environment. The phase change behaviour of the PCM may be utilised to provide thermal regulation as the nanocapsules may absorb heat during the solid to liquid phase transition (melting process) and release heat during the liquid to solid phase transition (solidification process). The PCM may undergo multiple cycles of absorbing heat during phase change from solid to liquid and releasing heat during the reverse phase change from liquid to solid without losing its thermal storage properties. This may allow for continuous cooling by repeatedly absorbing and releasing thermal energy.

[0052] PCMs may be organic phase change material, such as paraffin, sugar alcohols, fatty acids, fatty acid esters, salt hydrates, or molten salts. Paraffin refers to saturated hydrocarbons, typically derived from petroleum, including solid paraffin wax (used in candles, cosmetics, packaging) and liquid forms like paraffin oil, kerosene and petroleum jelly. Paraffin, such as paraffin wax, may exhibit phase change behaviour, melting from its solid state when heating and then releasing heat during the liquid to solid phase transition. For example, it was found that octadecane (a type of paraffin) may be encapsulated in a Si shell, and may exhibit phase change behaviour at a temperature range of about 20 °C to about 30 °C.

[0053] Sugar alcohols or polyols are hydrogenated forms of sugars, such as sorbitol, xylitol, erythritol and mannitol. They may be solid at room temperature and exhibit phase change behaviour. They may have higher melting temperatures at about 90 °C to about 160 °C as compared to paraffin wax and thus may be more suitable for higher temperature applications. Encapsulating a sugar alcohol in a shell may affect the phase change behaviour and may weaken the phase change behaviour.

[0054] A fatty acid is a carboxylic acid with an aliphatic chain, which may be saturated or unsaturated. Fatty acids may store and release large amounts of latent heat during the phase change process from solid to liquid and vice versa, demonstrating phase change behaviour. The temperature at which the phase change behaviour occurs may differ depending on the fatty acid or a combination thereof. Fatty acids may be encapsulated in a Si shell to form a nanocapsule.

[0055] Fatty acid esters are a type of ester that result from the combination of a fatty acid with an alcohol. Fatty acid esters may be monoglycerides, diglycerides, triglycerides, or fatty acid methyl esters. Fatty acid esters may exhibit phase change behaviour at atemperature of about 20 °C to about 70 °C, which may be affected by the fatty acid or alcohol that formed the fatty acid ester. For example, fatty acid esters may be encapsulated in polymeric shells and may exhibit phase change behaviour at temperatures of about 38 °C to about 40 °C.

[0056] Salt hydrates are ionic compounds that trap specific numbers of water molecules within their crystal structures to form solid crystalline materials, such as magnesium sulfate heptahydrate (Epsom salt), copper sulfate pentahydrate, sodium sulfate decahydrate (Glauber's salt), calcium chloride hexahydrate, and magnesium chloride hexahydrate. Salt hydrates may exhibit phase change behaviour at temperatures between about 20 °C to about 100 °C. For example, salt hydrates may be encapsulated in silica shells through electrohydrodynamic atomisation on a coaxial flow stream or through Pickering emulsion.

[0057] Molten salts are salts that are fully liquid at high temperatures, such as above 250 °C. For example, literature shows that KNO3 salt may be encapsulated in a Si shell and may be used for extremely high temperature applications at about 340 °C. The molten salts may be a mixture of different molten salts and may form a eutectic salt. A eutectic salt is a mixture of two or more salts that melts at a single, lower temperature than any of the individual components, known as the eutectic point. Molten salts and eutectic salts may exhibit phase change behaviour during melting and solidification and hence may be used as a phase change material. Depending on the mixture of the salts, a eutectic salt may exhibit phase change behaviour at temperatures of about 50 °C to about 300 °C.

[0058] For cosmetic and hair products, organic phase change materials may be preferred, such as paraffin wax, fatty acids, fatty acid esters and sugar alcohols or a combination thereof due to biocompatibility and may be non-irritating to skin and / or hair. They may also melt at temperatures of about 15 °C to about 45 °C, making them suitable for use for thermal regulation of hair, scalp, and / or skin. PCMs such as salt hydrates and molten salts may be used in other non-cosmetic and non-hair products due to their corrosivity and higher melting points.

[0059] In some embodiments, the phase change material is selected from paraffin, fatty acids, fatty acid esters, sugar alcohols, and a combination thereof.In some embodiments, the PCM is fatty acids. A fatty acid is a carboxylic acid with an aliphatic chain, which may be saturated or unsaturated. A saturated fatty acid has no double bonds and are straight chained. An unsaturated fatty acid may contain a single double bond (monounsaturated) or more than one double bond (polyunsaturated). Fatty acids may store and release large amounts of latent heat during the phase change process from solid to liquid and vice versa. The latent heat storage capacity of fatty acids may be higher than other PCMs. Fatty acids may undergo repeated melting and solidification cycles, and the phase change process may be reversible, making it suitable for applications that require cyclic thermal energy storage and release. Different fatty acids may have different melting and solidification temperatures, depending on the fatty acid composition. For example, as the carbon chain length of the fatty acid increases, the melting and solidification temperatures may increase. Saturated fatty acids with no double bonds in the carbon chain may have higher melting and solidification temperatures compared to unsaturated fatty acids. The presence of branching or isomeric forms in the fatty acid structure may also affect the melting and solidification temperatures. Branched fatty acids may have higher melting and solidification temperatures compared to linear fatty acids with the same carbon chain length.

[0060] The nanocapsules may be formed from an oil in water emulsion. The oil based PCMs may be mixed with a surfactant to modulate the interfacial tension of the oil droplets. This may allow for a more homogenous size distribution of droplets, and correspondingly nanocapsule size.

[0061] In some embodiments, the core comprises a phase change material configured to absorb heat from the hair, scalp, skin and / or an environment adjacent to the hair, scalp, and / or skin via conduction. When the temperature of the surrounding environment, such as the hair, scalp, skin and / or an environment adjacent to the hair, scalp, and / or skin, is higher than the melting range of the PCM, a temperature gradient may be established between the environment and the PCM. Due to the temperature gradient, heat energy may flow from the hotter environment to the cooler PCM core through conduction. Conduction is the transfer of heat through direct contact between the nanocapsules and the surrounding environment. As the heat energy is conducted into the core through the shell, the PCM may undergo a phase change from solid to liquid, absorbing the latent heat of fusion in the process. This may occur without an increase or with a small increase in temperature of the PCM as the energy absorbed may be used to break intermolecular bonds and overcome the phase transition. The removal of thermal energy from the surrounding environment may cause the temperature of thesurrounding environment to decrease, resulting in a cooling effect. The cooling effect may continue until the PCM has fully melted and reached the liquid state.

[0062] In some embodiments, the core comprises a phase change material configured to absorb heat from the hair, scalp, skin, and / or an environment adjacent to the hair, scalp, and / or skin. The rate of heat transfer from the surrounding environment may affect the rate of cooling and the duration of cooling as it may affect the rate at which the PCM melts. The rate of heat transfer may be affected by the temperature gradient, where a greater temperature gradient may result in a faster rate of heat transfer. The thermal conductivity of the core and the shell may also affect the rate of heat transfer, with a higher thermal conductivity facilitating a faster heat transfer to the core. Thinner shells may allow for faster heat transfer to the core, while thicker shells may impede the heat transfer process.

[0063] In some embodiments, the PCM comprises at least two fatty acids. Combining at least two fatty acids in specific proportions may create eutectic mixtures, which may have melting and solidification temperatures lower than the individual fatty acids. The proportions of the fatty acids in the eutectic mixtures may be altered to achieve the desired phase change temperature. For example, if the nanocapsule is to be used in countries with a hotter climate (about 35 °C to about 40 °C), the PCM may be one that melts at about 35 °C. If the nanocapsule is to be used in countries with a relatively cooler climate (about 30 °C to about 35 °C), the PCM may be one that melts at about 30 °C. The combination of fatty acids allows for fine tuning of phase change temperature and may allow the phase change temperature to be tailored for specific application requirements. A broader phase change temperature range (e.g. melting range) may be obtained as compared to the phase change temperature range of a single fatty acid. This may allow for a gradual and / or extended phase change, where the cooling effect may be extended over the duration at which the PCM melts. The combination of fatty acids with different latent heat of fusion may improve thermal cycling stability as it may reduce supercooling during the solidification process and reduce phase separation as the PCM undergoes repeated melting and solidification processes.

[0064] Accordingly, the present disclosure concerns a nanocapsule comprising a shell and a core;

[0065] wherein the core comprises a phase change material, the phase change material comprising at least two fatty acids.In some embodiments, the phase change material is oil based. An oil-based PCM may be less likely to leak or escape from the shell compared to more volatile or mobile PCM. The oil-based PCM may be compatible with and easily incorporated into personal care product formulations such as shampoos, conditioners and skincare products.

[0066] In some embodiments, the phase change material is a lipophilic material. A lipophilic material refers to a substance that has an affinity or attraction for lipids or non-polar substances, such as fats and oils. A lipophilic material may be non-polar, insoluble or slightly soluble in water. Fatty acids may be lipophilic due to the hydrocarbon chains and non-polar nature.

[0067] The phase change material may have a boiling point of more than about 50 °C, about 60 °C, about 70 °C, about 80 °C, about 90 °C, or about 100 °C. A boiling point refers to the temperature at which a material changes from a liquid to a gas. A boiling point of more than about 50 °C may ensure that the phase change material remains in a liquid or solid state at ambient temperatures. This may also reduce the risk of the phase change material from vaporising or undergoing undesirable phase changes during use.

[0068] In some embodiments, the phase change material is soluble in an organic medium.

[0069] In some embodiments, the at least two fatty acids are independently selected from Cs to C20 fatty acids. The carbon chain length of the fatty acids may affect the physical and thermal properties of the fatty acids. The melting and solidification temperatures of the fatty acids increases with an increase in the carbon chain length. Latent heat of fusion may also increase with carbon chain length. Longer-chain fatty acids may have higher latent heat of fusion and may be more effective for thermal energy storage. Longer-chain fatty acids may also exhibit higher thermal stability compared to shorter-chain fatty acids, allowing them to withstand higher temperatures without much degradation or decomposition. Shorter-chain fatty acids may have lower viscosities, making them easier to incorporate into emulsions to form a capsule. Different fatty acids may be selected to meet specific requirements of the nanocapsule, for example, for thermal regulation of skin, hair and / or scalp in different temperature climate.

[0070] In other embodiments, the at least two fatty acids are independently selected from Cs to Cis fatty acids, Cs to Cis fatty acids, Cs to CM fatty acids, Cs to C12 fatty acids, Cs to C10 fatty acids, Cs to C20 fatty acids, Cs to Cis fatty acids, Cs to Cis fatty acids, Cs to C14 fatty acids, Cs to C12 fatty acids, Cs to C10 fatty acids, C10 to C20 fatty acids, C10 to Cisfatty acids, Cw to Cw fatty acids, C to Ci4 fatty acids, Cw to C12 fatty acids, C12 to C20 fatty acids, C12 to Cw fatty acids, C12 to Cig fatty acids, C12 to C14 fatty acids, C14 to C20 fatty acids, C14 to Cis fatty acids, C 14 to Cig fatty acids, Cig to C20 fatty acids, Cig to Cis fatty acids, or Cis to C20 fatty acids. In some embodiments, the at least two fatty acids are independently selected from Cs to Cis fatty acids.

[0071] The at least two fatty acids may be saturated fatty acids, unsaturated fatty acids or a combination thereof. In some embodiments, the at least two fatty acids are saturated fatty acids. Saturated fatty acids may have higher melting and solidification temperatures compared to unsaturated fatty acids due to a more linear and tightly packed molecular structure. More energy may be required to overcome the intermolecular forces during phase change, resulting in the higher melting and solidification temperatures. Saturated fatty acids may have a higher degree of crystallinity, resulting in a more defined phase change transition compared to unsaturated fatty acids. This may allow for more precise temperature control for the cooling of the skin, hair and / or scalp.

[0072] In some embodiments, the at least two fatty acids are selected independently from Cg to C20 saturated fatty acids. In other embodiments, the at least two fatty acids are independently selected from Cg to Cis saturated fatty acids, Cg to Cig saturated fatty acids, Cg to C14 saturated fatty acids, Cg to C12 saturated fatty acids, Cg to Cw saturated fatty acids, Ca to C20 saturated fatty acids, Ca to Cw saturated fatty acids, Ca to Cw saturated fatty acids, Ca to C14 saturated fatty acids, Ca to C12 saturated fatty acids, Ca to Cw saturated fatty acids, Cw to C20 saturated fatty acids, C to Cis saturated fatty acids, Cw to Cw saturated fatty acids, C to C14 saturated fatty acids, Cw to C12 saturated fatty acids, C12 to C20 saturated fatty acids, C12 to Cis saturated fatty acids, C12 to C saturated fatty acids, C12 to C14 saturated fatty acids, C14 to C20 saturated fatty acids, C14 to Cw saturated fatty acids, C14 to Cw saturated fatty acids, Cw to C20 saturated fatty acids, C to Cw saturated fatty acids, or Cis to C20 saturated fatty acids. In some embodiments, the at least two fatty acids are independently selected from Cs to C is saturated fatty acids.

[0073] In some embodiments, the at least two fatty acids are characterised by a difference in a carbon chain length of at least 2 carbon. In other embodiments, the at least two fatty acids are characterised by a difference in a carbon chain length of at least 4 carbon, at least 6 carbon, at least 8 carbon, at least 10 carbon, at least 12 carbon, or at least 14 carbon.In some embodiments, the at least two fatty acids are characterised by a difference in a carbon chain length of 2 carbon to 15 carbon. In other embodiments, the at least two fatty acids are characterised by a difference in a carbon chain length of 2 carbon to 14 carbon, 2 carbon to 12 carbon, 2 carbon to 10 carbon, 2 carbon to 8 carbon, 2 carbon to 6 carbon, 2 carbon to 4 carbon, 4 carbon to 15 carbon, 4 carbon to 14 carbon, 4 carbon to 12 carbon, 4 carbon to 10 carbon, 4 carbon to 8 carbon, 4 carbon to 6 carbon, 6 carbon to 15 carbon, 6 carbon to 14 carbon, 6 carbon to 12 carbon, 6 carbon to 10 carbon, 6 carbon to 8 carbon, 8 carbon to 15 carbon, 8 carbon to 14 carbon, 8 carbon to 12 carbon, 8 carbon to 10 carbon, 10 carbon to 15 carbon, 10 carbon to 14 carbon, 10 carbon to 12 carbon, 12 carbon to 15 carbon, 12 carbon to 14 carbon, or 14 carbon to 15 carbon.

[0074] In some embodiments, the at least two fatty acids are selected from caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and a combination thereof. In some embodiments, the at least two fatty acids are myristic acid and stearic acid. In some embodiments, the at least two fatty acids are lauric acid and myristic acid.

[0075] In some embodiments, the melting temperature is a melting range. A phase change material comprising at least two fatty acids may have a melting range instead of a single melting point. The different molecular interactions and crystalline effects of the at least two fatty acids may result in a broader melting range as the at least two fatty acids may exhibit eutectic mixing, fractional melting, polymorphism and co-crystallisation. In eutectic mixing, the combination of the at least two fatty acids may result in a melting point that is lower than the individual melting points of the at least two fatty acids. This depression of the melting point may create a melting range as the fatty acids interact and influence each other's crystallisation behaviour. The PCM may exhibit fractional melting, where the fatty acid with a lower melting point may begin to melt first and the fatty acid with a higher melting point may remain solid until the temperature increases further. This may result in a gradual transition from solid to liquid, resulting in a melting range. The melting range may also be affected by polymorphism. Fatty acids may exist in different crystalline polymorphic forms, each with slightly different melting points. The at least two fatty acids may also co-crystallise, forming a mixed crystal structure with a distribution of melting points, resulting in a melting range.

[0076] In some embodiments, the phase change material is characterised by a melting range of about 15 °C to about 40 °C. In other embodiments, the melting range is about 15 °Cto about 35 °C, about 15 °C to about 30 °C, about 15 °C to about 25 °C, about 15 °C to about 20 °C, about 20 °C to about 40 °C, about 20 °C to about 35 °C, about 20 °C to about 30 °C, about 20 °C to about 25 °C, about 25 °C to about 40 °C, about 25 °C to about 35 °C, about 25 °C to about 30 °C, about 30 °C to about 40 °C, or about 30 °C to about 40 °C. In some embodiments, the melting range is about 30 °C to about 35 °C. In some embodiments, the melting temperature is a melting point. In some embodiments, the melting point is about 35 °C. In some embodiments, the melting point is about 30 °C.

[0077] In some embodiments, the phase change material is characterised by a solidification temperature range of about 15 °C to about 40 °C. In other embodiments, the solidification temperature range is about 15 °C to about 35 °C, about 15 °C to about 30 °C, about 15 °C to about 25 °C, about 15 °C to about 20 °C, about 20 °C to about 40 °C, about 20 °C to about 35 °C, about 20 °C to about 30 °C, about 20 °C to about 25 °C, about 25 °C to about 40 °C, about 25 °C to about 35 °C, about 25 °C to about 30 °C, about 30 °C to about 40 °C, or about 30 °C to about 40 °C. In some embodiments, the solidification temperature range is the melting range or melting point.

[0078] In some embodiments, the at least two fatty acids is characterized by a weight ratio of about 50:50 to about 90:10. For example, the fatty acid with a longer carbon chain may be myristic acid (C14) and the fatty acid with a shorter carbon chain may be lauric acid (C12). The weight ratio of myristic acid to lauric acid may be about 50:50 to about 90:10. In other embodiments, the weight ratio is about 50:50 to about 80:20, about 50:50 to about 70:30, about 50:50 to about 60:40, about 60:40 to about 90:10, about 60:40 to about 80:20, about 60:40 to about 70:30, about 70:30 to about 90:10, about 70:30 to about 80:20, or about 80:20 to about 90:10.

[0079] In some embodiments, the phase change material is characterised by a hydrophobicity of a certain degree. For example, the hydrophobicity of the phase change material may be measured using contact angle on a hydrophilic substrate, in which a contact angle of more than 90° indicates that the phase change material is hydrophobic, and a contact angle of more than 150° indicates that the phase change material is superhydrophobic.

[0080] In some embodiments, the core is characterised by a size of about 10 nm to about 1000 nm. In other embodiments, the size is about 10 nm to about 800 nm, about 10 nm to about 500 nm, about 10 nm to about 400 nm, about 10 nm to about 300 nm, about 10 nm to about 200 nm, about 10 nm to about 100 nm, about 10 nm to about50 nm, about 50 nm to about 1000 nm, about 50 nm to about 800 nm, about 50 nm to about 500 nm, about 50 nm to about 400 nm, about 50 nm to about 300 nm, about 50 nm to about 200 nm, about 50 nm to about 100 nm, about 100 nm to about 1000 nm, about 100 nm to about 800 nm, about 100 nm to about 500 nm, about 100 nm to about 400 nm, about 100 nm to about 300 nm, about 100 nm to about 200 nm, about 200 nm to about 1000 nm, about 200 nm to about 800 nm, about 200 nm to about 500 nm, about 200 nm to about 400 nm, about 200 nm to about 300 nm, about 300 nm to about 1000 nm, about 300 nm to about 800 nm, about 300 nm to about 500 nm, about 300 nm to about 400 nm, about 500 nm to about 1000 nm, about 500 nm to about 800 nm, or about 800 nm to about 1000 nm.

[0081] In some embodiments, the shell is a polymer shell and / or a silica shell. The shell material may influence the melting and solidification temperatures of the PCM, allowing for tailored thermal energy storage and release. The shell material may be a non-toxic material with sufficient mechanical strength to prevent leaks and premature breakage. The shell material may also be compatible with the core and any formulation that may comprise the nanocapsule. The shell material may be biodegradable and environmentally friendly. A polymer shell may help to regulate the thermal behaviour of the core, including during the phase change process. A polymer shell may also enhance the compatibility and dispersibility of the nanocapsule in different matrices such as aqueous solution or oils. A polymer shell may be a biodegradable polymer shell, such as polylactic acid shell, a synthetic polymer shell, such as polyethylene, polypropylene, or polyurethane, or a natural polymer shell, such as chitosan, alginate, or gelatin. A silica shell may have thermal stability and higher mechanical strength and rigidity compared to a polymer shell, offering better protection for the core. A silica shell may be less likely to break compared to a polymer shell. A combination of polymer and silica shells may be used to leverage the advantages of both materials.

[0082] In some embodiments, the shell is characterised by a thickness of about 1 nm to about 200 nm. The thickness of the shell may affect the mechanical strength of the shell and the transfer of heat from the external environment to the encapsulated core comprising the PCM. A thicker shell may provide more resistance to heat flow as heat travels a longer distance through the shell, slowing down the heat transfer rate. A thinner shell may reduce the resistance to heat flow to the PCM, allowing the PCM to effectively absorb and release heat for thermal regulation.In other embodiments, the thickness is about 1 nm to about 150 nm, about 1 nm to about 100 nm, about 1 nm to about 50 nm, about 1 nm to about 20 nm, about 1 nm to about 10 nm, about 10 nm to about 200 nm, about 10 nm to about 150 nm, about 10 nm to about 100 nm, about 10 nm to about 50 nm, about 1 nm to about 20 nm, about 20 nm to about 200 nm, about 20 nm to about 150 nm, about 20 nm to about 100 nm, about 20 nm to about 50 nm, about 50 nm to about 200 nm, about 50 nm to about 150 nm, about 50 nm to about 100 nm, about 100 nm to about 200 nm, about 100 nm to about 150 nm, or about 150 nm to about 200 nm. In some embodiments, the thickness is about 20 nm to about 100 nm. In some embodiments, the thickness is about 1 nm to about 30 nm.

[0083] In some embodiments, the shell is non-porous. A non-porous shell may provide a continuous barrier around the core, preventing any leakage or unwanted release of the core. A non-porous shell may minimise the potential for undesirable heat transfer pathways (e.g. through the pores) or thermal losses. A non-porous shell may also have higher mechanical strength and rigidity compared to a porous shell.

[0084] The nanocapsule may be non-breakable. The mechanical strength of the shell may be influenced by the shell thickness and structure. For example, a thicker shell may provide higher mechanical strength and resistance to deformation and / or breakage. A higher degree of cross-linking in the shell may enhance the mechanical strength of the shell and hence the nanocapsule. The strength of the interface between the PCM core and the shell may also affect the overall mechanical properties of the nanocapsule. A well-bonded and uniform interface may help to transfer stresses between the core and the shell when subject to a pressure or force, and improve the mechanical properties of the nanocapsule. In this regard, the shell may be of a certain thickness such that it is mechanically strong to withstand a certain amount of pressure or force. For example, when the nanocapsule is incorporated into a formulation, pressure or force may be exerted by a user when lathering hair or rubbing against a skin. The non-breakable shell may help to minimise any potential disruptions to the phase change behaviour due to physical stresses or force. The shell being non-breakable means that the phase change material is not releasable. This avoids an oily feel when the nanocapsules are applied to the hair, scalp and / or skin, which may be undesirable. Preferably, the thickness of the shell is about 20 nm to about 100 nm, balancing the need for a non-breakable shell and the need for effective heat transfer from the environment to the encapsulated core comprising the PCM. In some embodiments, the thickness of the shell is about 1 nm to about 30 nm, depending on the PCM used as a core.In some embodiments, the phase change material is not releasable from the nanocapsule.

[0085] In some embodiments, the core is separated from the shell by a layer of surfactant. The surfactant may improve the compatibility between the core and the shell, creating a stable interface and preventing phase separation between the core and the shell. The surfactant may also act as an emulsifier, helping to stabilise the core within the shell. The surfactant may lower interfacial tension between the core and water, allowing for easier emulsification of the lipophilic phase change material in water, enabling the formation of o / w emulsion.

[0086] In some embodiments, the layer of surfactant is a monolayer.

[0087] The layer of surfactant may be an ionic surfactant. In some embodiments, the layer of surfactant is selected from cetyltrimethylammonium chloride (CTAC), benzalkonium chloride, stearalkonium chloride, cetyltrimethylammonium Bromide (CTAB), benzyl dimethylamine, and a combination thereof.

[0088] In some embodiments, the nanocapsule is surface functionalised. Surface functionalisation refers to the modification of the surface of a material to introduce specific chemical, physical or biological properties, without changing the bulk of the material. The surface functionalisation may be a chemical functionalisation and / or physical functionalisation. This may improve stability of the nanocapsule.

[0089] In some embodiments, the nanocapsule is characterised by a particle size of about 70 nm to about 1500 nm. The particle size may affect the melting temperature of the phase change material. A smaller particle size may result in a lower melting temperature. Accordingly, the particle size may be adjusted to achieve the desired melting temperature.

[0090] In other embodiments, the particle size is about 70 nm to about 1000 nm, about 70 nm to about 900 nm, about 70 nm to about 800 nm, about 70 nm to about 600 nm, about 70 nm to about 400 nm, about 70 nm to about 200 nm, about 70 nm to about 100 nm, about 100 nm to about 1500 nm, about 100 nm to about 1000 nm, about 100 nm to about 900 nm, about 100 nm to about 800 nm, about 100 nm to about 600 nm, about 100 nm to about 400 nm, about 100 nm to about 200 nm, about 200 nm to about 1500nm, about 200 nm to about 1000 nm, about 200 nm to about 900 nm, about 200 nm to about 800 nm, about 200 nm to about 600 nm, about 200 nm to about 400 nm, about 400 nm to about 1500 nm, about 400 nm to about 1000 nm, about 400 nm to about 900 nm, about 400 nm to about 800 nm, about 400 nm to about 600 nm, about 600 nm to about 1500 nm, about 600 nm to about 1000 nm, about 600 nm to about 900 nm, or about 600 nm to about 800 nm. In some embodiments, the particle size is about 300 nm.

[0091] In some embodiments, the phase change material is characterised by a change in volume of about 8% to about 15% when the phase change material undergoes a phase transition. As the PCM undergoes the solid-to-liquid phase transition during melting, the PCM may exhibit a volume expansion. The change in volume may occur due to the structural rearrangement of the PCM, for example, the at least two fatty acids may be rearranged from a more closely packed and organised arrangement as a solid to a more disordered and less dense arrangement as a liquid. This leads to a volume expansion as the PCM melts. The PCM may exhibit a volume contraction when the PCM undergoes the liquid-to-solid phase transition during solidification, where the PCM becomes more ordered in the solid state. The nanocapsule may accommodate the change in volume during phase transition where the change may be accommodated within the shell to prevent structural damage or leakage. The shell may be flexible to the expansion and contraction of the core.

[0092] In other embodiments, the change in volume is about 8% to about 14%, about 8% to about 13%, about 8% to about 12%, about 8% to about 11%, about 8% to about 10%, about 10% to about 15%, about 10% to about 14%, about 10% to about 13%, about 10% to about 12%, about 10% to about 11%, about 11% to about 15%, about 11% to about 14%, about 11% to about 13%, about 11% to about 12%, about 12% to about 15%, about 12% to about 14%, about 12% to about 13%, about 13% to about 15%, about 13% to about 14%, or about 14% to about 15%.

[0093] In some embodiments, the phase change material is characterised by an increase in volume of about 8% to about 15% when the phase change material melts. In some embodiments, the phase change material is characterised by a decrease in volume of about 8% to about 15% when the phase change material solidifies.

[0094] In some embodiments, the nanocapsule is characterised by a temperature decrease of about 2.5 °C to about 5 °C when the phase change material melts. During the meltingprocess, the PCM absorbs the latent heat which is used to break intermolecular bonds and overcome the phase change. The PCM may remove heat from the surrounding environment, causing the temperature in the environment to decrease over time. In other embodiments, the temperature decrease is about 2.5 °C to about 4.5 °C, about 2.5 °C to about 4 °C, about 2.5 °C to about 3.5 °C, about 2.5 °C to about 3 °C, about 3 °C to about 5 °C, about 3 °C to about 4.5 °C, about 3 °C to about 4 °C, about 3 °C to about 3.5 °C, about 3.5 °C to about 5 °C, about 3.5 °C to about 4.5 °C, about 3.5 °C to about 4 °C, about 4 °C to about 5 °C, or about 4 °C to about 4.5 °C.

[0095] In some embodiments, the phase change material is characterised by a melting duration of about 1 minute to about 100 minutes. In some embodiments, the phase change material is characterised by a melting duration of about 10 minutes to about 100 minutes. A shorter melting duration may allow the nanocapsule to cycle through multiple solid-liquid transitions in a relatively short period of time. A longer melting duration may result in a longer cooling period. In other embodiments, the duration is about 1 minute to about 80 minutes, about 1 minute to about 60 minutes, about 1 minute to about 40 minutes, about 1 minute to about 20 minutes, about 1 minute to about 10 minutes, about 10 minutes to about 80 minutes, about 10 minutes to about 60 minutes, about 10 minutes to about 40 minutes, about 10 minutes to about 20 minutes, about 20 minutes to about 100 minutes, about 20 minutes to about 80 minutes, about 20 minutes to about 60 minutes, about 20 minutes to about 40 minutes, about 40 minutes to about 100 minutes, about 40 minutes to about 80 minutes, or about 40 minutes to about 60 minutes. In some embodiments, the phase change material is characterised by a melting duration of about 1 minute to about 10 minutes.

[0096] In some embodiments, the nanocapsule is configured to withstand at least two heatmelt cycles without leaching of the phase change material. A heat-melt cycle refers to a process in which a material is heated until it melts, then cooled until it solidifies. For example, the PCM within the nanocapsule is heated until it melts, transiting from a solid state to a liquid state and then back to a solid state when the PCM is cooled. When the nanocapsule is exposed to heat, increasing the temperature of the PCM, the PCM melts and absorbs latent heat in the process when the temperature reaches the melting temperature of the PCM. When the nanocapsule loses heat to the surrounding environment, the temperature of the PCM decreases, resulting in the transition of the PCM from a liquid state to a solid state, completing a heat-melt cycle. The PCM may undergo at least two-heat melt cycles or multiple heat-melt cycles and the cyclic process of heating and cooling the PCM may cause the PCM to undergo repeated phase changesbetween the solid and liquid states. The nanocapsule may be able to withstand at least two heat-melt cycles without failing or compromising its integrity. The nanocapsule may be able to withstand at least two heat-melt cycles without leaching of the phase change material due to effective encapsulation of the phase change material within the shell. This may improve the long-term performance and reliability of the nanocapsule. In other embodiments, the nanocapsule is configured to withstand at least three heat-melt cycles, at least four heat-melt cycles, at least five heat-melt cycles, at least six heatmelt cycles, at least seven heat-melt cycles, at least eight heat-melt cycles, at least nine heat-melt cycles, or at least ten heat-melt cycles without leaching of the phase change material.

[0097] In some embodiments, the nanocapsule is configured to withstand at least two heatmelt cycles without leaching of the phase change material within a duration of about 1 hour to about 24 hours. The nanocapsule may quickly absorb and release heat as needed, with each heat-melt cycle occurring within a relatively short period of time of about 1 minute to about 10 minutes. The melting duration of the phase change material may also be about 1 minute to about 10 minutes. The at least two heat-melt cycles may occur within a 24-hour period, such as within a duration of about 1 hour to about 24 hours. The nanocapsule may be exposed to fluctuating temperatures over the course of a day or during use, and the ability to withstand the fluctuating temperatures may aid in maintaining the thermal regulation performance.

[0098] In other embodiments, the nanocapsule is configured to withstand at least three heatmelt cycles, at least four heat-melt cycles, at least five heat-melt cycles, at least six heat-melt cycles, at least seven heat-melt cycles, at least eight heat-melt cycles, at least nine heat-melt cycles, or at least ten heat-melt cycles without leaching of the phase change material within a duration of about 1 hour to about 20 hours, about 1 hour to about 15 hours, about 1 hour to about 10 hours, about 4 hours to about 24 hours, about 4 hours to about 20 hours, about 4 hours to about 15 hours, about 4 hours to about 10 hours, about 10 hours to about 24 hours, about 10 hours to about 20 hours, about 10 hours to about 15 hours, about 15 hours to about 24 hours, about 15 hours to about 20 hours, or about 20 hours to about 24 hours.

[0099] In some embodiments, the nanocapsule is configured to not leach the phase change material at a temperature range of about 15 °C to about 40 °C. In other embodiments, the temperature range is about 15 °C to about 35 °C, about 15 °C to about 30 °C, about 15 °C to about 25 °C, about 15 °C to about 20 °C, about 20 °C to about 40 °C, about20 °C to about 35 °C, about 20 °C to about 30 °C, about 20 °C to about 25 °C, about 25 °C to about 40 °C, about 25 °C to about 35 °C, about 25 °C to about 30 °C, about 30 °C to about 40 °C, about 30 °C to about 35 °C, or about 35 °C to about 40 °C.

[0100] In some embodiments, the nanocapsule is characterised by a thermal conductivity of about 0.1 W / m-K to about 0.3 W / m-K. Thermal conductivity is a measure of a material's ability to conduct heat. It quantifies how easily heat may pass through a material when there is a temperature difference. A PCM with lower thermal conductivity may have less efficient heat transfer through the PCM. The presence of functional groups, degree of crystallinity and impurities may affect the thermal conductivity. A low thermal conductivity may limit the rate of heat transfer and the efficiency of the phase change process. The thermal conductivity of the PCM comprising at least two fatty acids may be about 0.15 W / m-K to about 0.25 W / m-K. The thermal conductivity may be increased by encapsulating the PCM core in a shell with higher thermal conductivity, such as a silica shell. A silica shell may have a thermal conductivity of about 0.1 W / m-K to about 0.3 W / m-K. In other embodiments, the thermal conductivity is about 0.1 W / m-K to about 0.25 W / m-K, about 0.1 W / m-K to about 0.22 W / m-K, about 0.1 W / m-K W / m-K to about 0.2 W / m-K, about 0.1 W / m-K to about 0.15 W / m-K, about 0.15 W / m-K to about 0.3 W / m-K, about 0.15 W / m-K to about 0.25 W / m-K, about 0.15 W / m-K to about 0.22 W / m-K, about 0.15 W / m-K to about 0.2 W / m-K, about 0.2 W / m-K to about 0.3 W / m-K, about 0.2 W / m-K to about 0.25 W / m-K, about 0.2 W / m-K to about 0.22 W / m-K, about 0.22 W / m-K to about 0.3 W / m-K, or about 0.22 W / m-K to about 0.25 W / m-K.

[0101] In some embodiments, the nanocapsule is characterised by a latent heat of fusion of about 150 kJ / kg to about 250 kJ / kg. Latent heat ef fusion refers to the specific amount of heat energy required to change the state of a material from a solid to a liquid, or vice versa, without a change in temperature. This phase change process may occur when the PCM solid absorbs heat, causing its particles to gain energy and overcome the forces holding them in a rigid structure. PCM with higher latent heat of fusion may allow the PCM to store and release a larger amount of thermal energy. In other embodiments, the latent heat of fusion is about 150 kJ / kg to about 225 kJ / kg, about 150 kJ / kg to about 200 kJ / kg, about 200 kJ / kg to about 250 kJ / kg, about 200 kl / kg to about 225 kl / kg, or about 225 kl / kg to about 250 kJ / kg.

[0102] The nanocapsule may be formed via an oil-in-water emulsion, in-situ polymerisation, coacervation, or sol-gel encapsulation. In some embodiments, the nanocapsule is formed via an oil-in-water emulsion.The present disclosure also concerns a method of forming a nanocapsule, comprising: a) emulsifying an oil phase comprising a phase change material in an aqueous medium in the presence of a surfactant to obtain an oil-in-water emulsion, the surfactant is configured to form a layer of surfactant at a surface of a microemulsion droplet; and

[0103] b) mixing a precursor into the oil-in-water-emulsion to form a shell around the droplet in order to form the nanocapsule;

[0104] wherein the phase change material comprises at least two fatty acids.

[0105] An oil-in-water emulsion may help to disperse the PCM in an aqueous continuous phase, preventing agglomeration of the PCM. The shell precursor undergoes interfacial polymerisation at the oil-water interface.

[0106] In some embodiments, the method is performed at a temperature of about 30 °C to about 100 °C. In other embodiments, the temperature is about 30 °C to about 80 °C, about 30 °C to about 60 °C, about 30 °C to about 40 °C, about 40 °C to about 100 °C, about 40 °C to about 80 °C, about 40 °C to about 60 °C, about 60 °C to about 100 °C, or about 60 °C to about 80 °C. In some embodiments, the temperature is about 40 °C to about 80 °C.

[0107] In some embodiments, the oil-in-water emulsion is characterised by a wt% of PCMs (or fatty acids) of about 0.1 wt% to about 5 wt% relative to the oil-in-water emulsion. In other embodiments, the wt% of fatty acids is about 0.1 wt% to about 4 wt%, about 0.1 wt% to about 3 wt%, about 0.1 wt% to about 2 wt%, about 0.1 wt% to about 1 wt%, about 1 wt% to about 5 wt%, about 1 wt% to about 4 wt%, about 1 wt% to about 3 wt%, about 1 wt% to about 2 wt%, about 2 wt% to about 5 wt%, about 2 wt% to about 4 wt%, about 2 wt% to about 3 wt%, about 3 wt% to about 5 wt%, or about 3 wt% to about 4 wt% relative to the oil-in-water emulsion. In some embodiments, the wt% of fatty acids is about 0.5 wt% to about 2 wt% relative to the oil-in-water emulsion.

[0108] In some embodiments, the oil-in-water emulsion is characterised by a wt% of surfactant of about 1 wt% to about 10 wt% relative to the oil-in-water emulsion. In other embodiments, the wt% of surfactant is about 1 wt% to about 8 wt%, about 1 wt% to about 6, about 1 wt% to about 4 wt%, about 1 wt% to about 2 wt%, about 2 wt% to about 10 wt%, about 2 wt% to about 8 wt%, about 2 wt% to about 6 wt%, about 2 wt% to about 4 wt%, about 4 wt% to about 10 wt%, about 4 wt% to about 8 wt%, about4 wt% to about 6 wt%, about 6 wt% to about 10 wt%, or about 6 wt% to about 8 wt% relative to the oil-in-water emulsion. In some embodiments, the wt% of surfactant is about 1.5 wt% to about 7.5 wt% relative to the oil-in-water emulsion.

[0109] In some embodiments, the oil-in-water emulsion is characterised by a wt% of water of about 85 wt% to about 99 wt% relative to the oil-in-water emulsion. In other embodiments, the wt% of water is about 85 wt% to about 95 wt%, about 85 wt% to about 90 wt%, about 90 wt% to about 99 wt%, about 90 wt% to about 95 wt%, or about 95 wt% to about 99 wt% relative to the oil-in-water emulsion. In some embodiments, the wt% of water is about 90 wt% to about 98 wt% relative to the oil-in-water emulsion.

[0110] In some embodiments, the microemulsion droplet is characterised by a droplet size of about 10 nm to about 500 nm. In other embodiments, the droplet size is about 10 nm to about 400 nm, about 10 nm to about 300 nm, about 10 nm to about 200 nm, about 10 nm to about 100 nm, about 10 nm to about 50 nm, about 50 nm to about 500 nm, about 50 nm to about 400 nm, about 50 nm to about 300 nm, about 50 nm to about 200 nm, about 50 nm to about 100 nm, about 100 nm to about 500 nm, about 100 nm to about 400 nm, about 100 nm to about 300 nm, about 100 nm to about 200 nm, about 200 nm to about 500 nm, about 200 nm to about 300 nm, about 200 nm to about 400 nm, about 300 nm to about 500 nm, or about 300 nm to about 400 nm.

[0111] In some embodiments, step a) further comprises dispersing the phase change material by high-speed homogenisation and / or sonication. The high-speed homogenisation and / or sonification may supply energy to disperse the oil phase of the PCM in the water phase in order to form an oil-in-water emulsion. High speed homogenisation may involve a high shear device, such as a rotor-stator homogeniser, to break down the oil phase into small droplets and disperse them into the continuous water phase. Sonication may involve using high frequency sound waves to create cavitation and intense shear forces within the water phase. Sonication may break down the oil phase into small droplets and disperse them homogeneously in the water phase. The high shear forces generated from the high-speed homogenisation and / or sonification may reduce the size of the microemulsion droplet, leading to a stable and finely dispersed emulsion.

[0112] In some embodiments, the method is characterised by a homogenisation speed of about 5000 rpm to about 30000 rpm. In other embodiments, the speed is about 5000 rpm to about 25000 rpm, about 5000 rpm to about 20000 rpm, about 5000 rpm to about 15000rpm, about 5000 rpm to about 10000 rpm, about 10000 rpm to about 30000 rpm, about 10000 rpm to about 25000 rpm, about 10000 rpm to about 20000 rpm, about 10000 rpm to about 15000 rpm, about 15000 rpm to about 30000 rpm, about 15000 rpm to about 25000 rpm, about 15000 rpm to about 20000 rpm, about 20000 rpm to about 30000 rpm, or about 20000 rpm to about 25000 rpm.

[0113] In some embodiments, the method is characterised by a sonification frequency of about 20 kHz to about 2000 kHz. In other embodiments, the sonication frequency is about 20 kHz to about 1500 kHz, about 20 kHz to about 1000 kHz, about 20 kHz to about 500 kHz, about 20 kHz to about 100 kHz, about 100 kHz to about 2000 kHz, about 100 kHz to about 1500 kHz, about 100 kHz to about 1000 kHz, about 100 kHz to about 500 kHz, about 500 kHz to about 2000 kHz, about 500 kHz to about 1500 kHz, about 500 kHz to about 1000 kHz, about 1000 kHz to about 2000 kHz, about 1000 kHz to about 1500 kHz, or about 1500 kHz to about 2000 kHz.

[0114] In some embodiments, the oil-in-water emulsion is characterised by a dilution of about 2 times to about 10 times in water after step a). The water may be pre-warmed water. Diluting the emulsion may help to improve the overall stability of the emulsion by reducing the concentration of the dispersed oil phase. This may reduce droplet coalescence, leading to a more stable emulsion. In other embodiments, the dilution is about 2 times to about 8 times, about 2 times to about 6 times, about 2 times to about 4 times, about 4 times to about 10 times, about 4 times to about 8 times, about 4 times to about 6 times, about 6 times to about 10 times, about 6 times to about 8 times, or about 8 times to about 10 times.

[0115] In some embodiments, the precursor is selected from a polymer precursor and a silica precursor.

[0116] In some embodiments, the silica precursor is selected from tetraorthosilicate, tetramethoxysilane, tetrabutylorthosilicate, methyltriethoxysilane, phenyltriethoxysilane, sodium silicate and a combination thereof.

[0117] In some embodiments, step b) further comprises stirring. Stirring may help to ensure that the silica precursor is evenly distributed throughout the emulsion, facilitating the formation of a homogeneous silica shell with uniform thickness around each of microemulsion droplet. A silica precursor may undergo a condensation reaction to forma silica shell and stirring may ensure that the silica condenses and deposits evenly on the surface of the microemulsions.

[0118] In some embodiments, the stirring is performed for a duration of about 5 minutes to about 150 minutes. In other embodiments, the duration is about 5 minutes to about 120 minutes, about 5 minutes to about 100 minutes, about 5 minutes to about 50 minutes, about 5 minutes to about 10 minutes, about 10 minutes to about 150 minutes, about 10 minutes to about 120 minutes, about 10 minutes to about 100 minutes, about 10 minutes to about 50 minutes, about 50 minutes to about 150 minutes, about 50 minutes to about 120 minutes, about 50 minutes to about 100 minutes, about 100 minutes to about 150 minutes, or about 100 minutes to about 120 minutes. In some embodiments, the stirring is performed for a duration of about 10 minutes to about 120 minutes.

[0119] In some embodiments, the method further comprises a quenching and purification step after step b). Quenching may stop the condensation process of the shell formation by adding an acid or a base, preventing uncontrolled growth of the shell. Purification may involve washing the mixture of emulsion and precursor to remove excess unreacted precursor to obtain the nanocapsules.

[0120] The present disclosure also concerns a method of cooling hair, scalp and / or skin, comprising applying a formulation to a hair, scalp and / or skin;

[0121] wherein the formulation comprises nanocapsules as disclosed herein.

[0122] In some embodiments, the formulation comprises nanocapsules at a wt% of about 0.1 wt% to about 5 wt% relative to the formulation. A higher wt% of nanocapsules may provide a greater cooling effect while a lower wt% of nanocapsules may prevent agglomeration of the nanocapsules in the formulation. When the wt% of nanocapsules is too high, such as more than about 5%, the cooling effect may not be significantly enhanced and the overall texture, feel or appearance of the formulation when used in a product may be affected. The wt% of nanocapsules may be adjusted to achieve the desired cooling effect.

[0123] In other embodiments, the wt% is about 0.1 wt% to about 4 wt%, about 0.1 wt% to about 3 wt%, about 0.1 wt% to about 2 wt%, about 0.1 wt% to about 1 wt%, about 0.1 wt% to about 0.5 wt%, about 0.5 wt% to about 5 wt%, about 0.5 wt% to about 4 wt%, about 0.5 wt% to about 3 wt%, about 0.5 wt% to about 2 wt%, about 0.5 wt%to about 1 wt%, about 1 wt% to about 5 wt%, about 1 wt% to about 4 wt%, about 1 wt% to about 3 wt%, about 1 wt% to about 2 wt%, about 2 wt% to about 5 wt%, about 2 wt% to about 4 wt%, about 2 wt% to about 3 wt%, about 3 wt% to about 5 wt%, about 3 wt% to about 4 wt%, or about 4 wt% to about 5 wt%. In some embodiments, the wt% is about 1 wt%.

[0124] This wt% of nanocapsule in the formulation is sufficient to allow a user to experience a temperature change of about 0.1 °C to about 10 °C.

[0125] The present disclosure also concerns a nanocapsule as disclosed herein. The nanocapsule comprises a shell and a core, wherein the core comprises a phase change material configured to absorb heat from the hair, scalp, skin, and / or an environment adjacent to the hair, scalp, and / or skin. In some embodiments, the phase change material comprises at least two fatty acids.

[0126] The present disclosure also concerns a formulation, comprising nanocapsules as disclosed herein. The present disclosure also concerns a method of formulating a formulation as disclosed herein.

[0127] In some embodiments, the formulation further comprises an excipient and / or a solvent.

[0128] The formulation may contain any suitable carriers, diluents or excipients. These include all conventional solvents, dispersion media, fillers, solid carriers, coatings, antifungal and antibacterial agents, dermal penetration agents, surfactants, isotonic and absorption agents and the like. Excipients include any and all solvents, dispersion media, inert diluents, or other liquid vehicles, dispersion or suspension aids, granulating agents, surface active agents, disintegrating agents, isotonic agents, thickening or emulsifying agents, preservatives, binding agents, lubricants, buffering agents, oils, and the like, as suited to the particular dosage form desired. Various excipients used in formulating pharmaceutical compositions and known techniques for the preparation thereof is disclosed in G. A. R. Remington: The Science and Practice of Pharmacy, 21st ed. (2006), Lippincott Williams & Wilkins. Except insofar as any conventional excipient is incompatible with a substance or its derivatives, such as by producing any undesirable biological effect or otherwise interacting in a deleterious manner with any other component(s) of the formulation, its use is contemplated to be within the scope of this disclosure.Excipients such as colouring agents, coating agents, and perfuming agents can be present in the formulation, according to the judgment of the formulator.

[0129] The solvent may be an aqueous medium. The term 'aqueous medium' used herein refers to a water based solvent or solvent system, and which comprises of mainly water. Such solvents can be either polar or non-polar, and / or either protic or aprotic. Solvent systems refer to combinations of solvents which resulting in a final single phase. Both 'solvents' and 'solvent systems' can include, and is not limited to, pentane, cyclopentane, hexane, cyclohexane, benzene, toluene, dioxane, chloroform, diethylether, dichloromethane, tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, dimethyl sulfoxide, nitromethane, propylene carbonate, formic acid, butanol, isopropanol, propanol, ethanol, methanol, acetic acid, ethylene glycol, diethylene glycol or water. Water based solvent or solvent systems can also include dissolved ions, salts and molecules such as amino acids, proteins, sugars and phospholipids. Such salts may be, but not limited to, sodium chloride, potassium chloride, ammonium acetate, magnesium acetate, magnesium chloride, magnesium sulfate, potassium acetate, potassium chloride, sodium acetate, sodium citrate, zinc chloride, HEPES sodium, calcium chloride, ferric nitrate, sodium bicarbonate, potassium phosphate and sodium phosphate.

[0130] The formulation may be for use in various products such as hair care products and skin products. Hair care products may be leave-in conditioners, rinse-off conditioners, or hair sprays. Skin products may be sunblocks, sun lotions, body lotions, or face lotions.

[0131] Examples

[0132] The present disclosure uses phase change materials (PCMs) contained within nanocapsules to provide a cooling effect to the user. PCMs are substances which absorb / release large amounts of energy when they go through a change in their physical state e.g. melting / freezing, providing the benefits of cooling / heating.

[0133] The composition of the PCM is chosen based on the phase change temperature of interest. For example, if the nanocapsule is to be used in countries with a hotter climate (35 - 40 °C), the PCM chosen may be one that melts at ~35 °C, and if the nanocapsule is to be used in countries with a relatively cooler climate (30 - 35 °C), the PCM chosen may be one that melts at ~30 °C. A combination of PCMs may be used such that its combination thereof has a desired temperature. As such, a series of nanocapsules that work at different temperature ranges may be developed. These nanocapsules may bemixed into hair care products such as leave-in conditioners, hair sprays etc. This is also different from heat protectant sprays in which that technology is designed to buffer the much higher temperatures used in straightening irons etc.

[0134] The cooling effect may be from actual cooling via the melting of the PCM, per se, and not a change in the sensation of cooling. The nanocapsule does not combine or utilize an evaporative cooling or a neurosensory component that contributes to the cooling sensation felt by skin and the cooling effect may be contributed by PCM only. The PCM may be encapsulated to prevent leaks or changes in feel or formulation consistency. Having the nanocapsule in a nanoparticle form allows flexibility in adoption of technology, i.e. mixed into leave-in conditioners, serums, instead of standalone as a fixed formulation.

[0135] According to Figure 1, the PCM may be encapsulated in a nanocapsule. This may be done by forming oil-in-water (o / w) microemulsions using a suitable PCM as the oil phase and stabilised by a suitable surfactant. Energy is externally supplied to disperse the oil phase in the water phase through high-speed homogenisation or sonication. Subsequently, the nanocapsule precursors are added to form a shell around the microemulsion droplets.

[0136] The PCM composition is carefully chosen and engineered to melt in a suitable temperature range. A mixture of different PCM-containing nanocapsules may be combined to achieve a cooling effect over a wider temperature range. The nanocapsule shell is synthesized to prevent leakage of PCM when melted. The nanocapsule may be able to withstand multiple heat-melt cycles to last throughout the day without leakage.

[0137] The PCM used were combinations of fatty acids e.g. capric acid, lauric acid, myristic acid, stearic acid, but not limited to these. The surfactant used was cetyltrimethylammonium chloride (CTAC) or similar surfactants. The nanocapsule shell was polymer or silica-based, formed using the silica precursor tetraorthosilicate (TEOS) or similar precursors or other appropriate nanocapsule materials.

[0138] For example, the formulation of the o / w emulsion may be:

[0139] • 0.5 - 2.0 % fatty acid

[0140] • 1.81 - 7.24% surfactant

[0141] • 90.7 - 97.6% waterAs an example, through using a silica-based nanocapsule shell:

[0142] The obtained emulsion was diluted 2 - 10 times in pre-warmed water. Tetraorthosilicate / ethanol mixture (1: 1 v / v) was added dropwise under vigorous stirring at 40 - 80 °C to obtain a final TEOS proportion of 0.5 - 5%. The mixture was left to stir for 10 - 120 min, after which it was quickly quenched and purified immediately. The shell thickness of the nanocapsules is about 1 nm to about 30 nm.

[0143] A test was set up in which two of PCM formulations (60LA40MASi and LASi) were compared with two negative control formulations (OASi and SASi). OASi refers to nanocapsules with oleic acid as the PCM within a Si shell. SASi comprises nanocapsules with stearic acid as the PCM within a Si shell. As the bulk melting temperatures of oleic acid and stearic acid are beyond the intended working temperature range, at about 13 °C to about 14 °C and at about 69 °C to about 70 °C respectively, OASi and SASi were used as negative control formulations. 60LA40MASi refers to nanocapsules with 60% LA (lauric acid) and 40% MA (myristic acid) as the PCM within a Si shell and LASi refers to nanocapsules with 100% LA within a Si shell. According to literature, a 60LA-40MA mixture has a melting temperature of about 35 °C, and the preliminary data of 100%LA in a nanocapsule demonstrates a melting temperature of about 34 °C. These are within the intended working temperature of the technology.

[0144] The temperature change with time of the formulations were compared against a blank control (Figure 2). Preliminary data below shows that in both 60LA40MASi and LASi, there was a larger temperature change compared to a blank control, than for the OASi and SASi versus a blank control.

[0145] In terms of safety, appropriate PCMs may be chosen. The PCMs in the applicable temperature range are naturally occurring in some food and are used in various cosmetic products already. Silica is also generally regarded as safe (GRAS) and are used in many cosmetic products too. Silica of this size (~500nm) are also deemed safe as they are too big to penetrate skin.

[0146] The nanocapsules may be added into hair care products e.g. leave-in conditioners, rinse-off conditioners, hair sprays, scalp sprays, and dry shampoos, and into skin products e.g. sunblocks, after sun lotions, makeup, deodorants, and anti-perspirants.

[0147] As shown in Figure 3, the nanocapsules may be customisable with flexible melting temperatures and melting temperature ranges. The nanocapsules may be able towithstand multiple heat-cool cycles. The nanocapsules may be leak-proof as the PCM is not releasable from the nanocapsules. Compared to other products that may provide a cooling effect, the nanocapsules may be menthol-free, which may result in less potential for skin and / or eye irritation. The cooling effect may be from actual cooling via the melting of the PCM, per se, and not a change in the sensation of cooling. As a result, the cooling effect may be longer lasting.

[0148] Figure 4 represents an example of 2 heating / cooling cycles where the designed melting temperature is at e.g. 32 °C. At external temperatures of below 32 °C, the hair / skin with nanocapsules applied behaves the same as hair / skin without nanocapsules. As the external temperature rises, the temperature of the hair / skin without nanocapsules follows accordingly till it reaches the external temperature. However, in the case of hair / skin with nanocapsules, when external temperatures reach the designed melting temperature (32 °C), the nanocapsule starts to absorb the heat energy more, and remains at 32 °C till the PCM is fully melted, then the temperature of the hair / skin will rise as per normal, until it is cooled again, in which the PCM in the nanocapsule will cool and solidify again.

[0149] Study of cooling effect of the nanocapsules (Figure 5)

[0150] Procedure:

[0151] 1. Temperature set to fixed temp in Styrofoam box using the heating fan (monitored with heating fan & thermometer).

[0152] 2. Thermostat probe covered with treated / untreated hair outside the setup.

[0153] 3. Hair switch + probe quickly placed into holder and temperature recorded every 10s.

[0154] • The hair may be treated with nanocapsules comprising different PCM formulations (labelled as A and B) or with controls.

[0155] ■ Controls: commercial leave-ln conditioner (commercial), surfactant, untreated hair (bare).

[0156] Surfactant refers to CTAC of the same wt% used in the nanocapsule formulation. The surfactant is used as a control to determine whether a temperature buffer effect is due to the fatty acid or the CTAC. The results showed that any temperature buffer effect is due to the fatty acid and not the CTAC.

[0157] As shown in Figure 6, nanocapsules comprising A and nanocapsules comprising B buffer the temperature between surroundings and probe (scalp) more than the controls. Hair treated with nanocapsules comprising A has a slower temperature rise than untreatedhair in 30 ~ 32 °C temperature range. A refers to a silica nanocapsule encapsulating 100% lauric acid (bulk melting temp ~44 °C), and B refers to silica nanocapsule encapsulating 100% capric acid (bulk melting temp ~ 31°C).

[0158] The experiment also shows that melting temperature will shift depending on size of nanocapsule, and formulation A in this case, works well at the intended temperature range. Nanocapsules comprising A and B were approximately 300 nm in size. It is found that the melting temperature decreases as the size of the nanocapsule decreases.

[0159] As shown in Figure 6, when the nanocapsule was subjected to a temperature of 35 °C, the rate of temperature rise was lower than the rate of temperature rise for bare hair when the temperature of the nanocapsule is between about 30 °C to about 32 °C. The rate of temperature rise is faster as hair temperature is further away from the set temperature of 35 °C and slows down as the temperature nears the set temperature of 35 °C. This is regardless of bare hair or hair coated with nanocapsules. Figure 6 shows that the hair temperature, when coated with LA-nanocapsules, rises slower than without nanocapsule coating at the intended temperature range (30~32 °C). The negative rate of temperature rise is more likely due to fluctuations especially nearing the set temperature, rather than due to melting, as some of the bare hair data points are negative.

[0160] It will be appreciated that many further modifications and permutations of various aspects of the described embodiments are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.

[0161] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0162] Throughout this specification and the claims which follow, unless the context requires otherwise, the phrase "consisting essentially of", and variations such as "consists essentially of" will be understood to indicate that the recited element(s) is / are essential i.e. necessary elements of the invention. The phrase allows for the presence of other non-recited elements which do not materially affect the characteristics of the inventionbut excludes additional unspecified elements which would affect the basic and novel characteristics of the method defined.

[0163] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

Claims1. Use of a nanocapsule for thermal regulation of hair, scalp and / or skin, comprising a step of contacting the nanocapsule with the hair, scalp and / or skin;wherein the nanocapsule comprises a shell and a core;wherein the core comprises a phase change material configured to absorb heat from the hair, scalp, skin, and / or an environment adjacent to the hair, scalp, and / or skin.

2. The use according to claim 1, wherein the phase change material comprises at least two fatty acids.

3. The use according to claim 1 or 2, wherein the phase change material is a lipophilic material.

4. The use according to claim 2 or 3, wherein the at least two fatty acids are independently selected from Cs to C20 fatty acids.

5. The use according to any one of claims 2 to 4, wherein the at least two fatty acids are saturated fatty acids.

6. The use according to any one of claims 2 to 5, wherein the at least two fatty acids are selected from caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and a combination thereof.

7. The use according to any one of claims 1 to 6, wherein the phase change material is characterised by a melting range of about 15 °C to about 40 °C.

8. The use according to any one of claims 1 to 7, wherein the phase change material is characterised by a solidification temperature of about 15 °C to about 40 °C.

9. The use according to any one of claims 1 to 8, wherein the core is characterised by a size of about 10 nm to about 1000 nm.

10. The use according to any one of claims 1 to 9, wherein the shell is a polymer shell and / or a silica shell.

11. The use according to any one of claims 1 to 10, wherein the shell is characterised by a thickness of about 1 nm to about 200 nm.

12. The use according to any one of claims 1 to 11, wherein the shell is non-porous.

13. The use according to any one of claims 1 to 12, wherein the phase change material is not releasable from the nanocapsule.

14. The use according to any one of claims 1 to 13, wherein the nanocapsule is characterised by a particle size of about 70 nm to about 1500 nm.

15. The use according to any one of claims 1 to 14, wherein the nanocapsule is characterised by a temperature decrease of about 2.5 °C to about 5 °C when the phase change material melts.

16. The use according to any one of claims 1 to 15, wherein the nanocapsule is characterised by a melting duration of about 1 minute to about 100 minutes.

17. The use according to any one of claims 1 to 16, wherein the nanocapsule is configured to withstand at least two heat-melt cycles without leaching of the phase change material.

18. The use according to any one of claims 1 to 17, wherein the nanocapsule is configured to not leach the phase change material at a temperature range of about 15 °C to about 40 °C.

19. The use according to any one of claims 1 to 18, wherein the nanocapsule is characterised by a thermal conductivity of about 0.1 W / m-K to about 0.3 W / m-K.

20. The use according to any one of claims 1 to 19, wherein the nanocapsule is characterised by a latent heat of fusion of about 150 kj / kg to about 250 kJ / kg.

21. A method of cooling hair, scalp and / or skin, comprising applying a formulation to a hair, scalp and / or skin;wherein the formulation comprises nanocapsules according to any one of claims 1 to22. The method according to claim 21, wherein the formulation comprises nanocapsules at a wt% of about 0.5 wt% to about 5 wt% relative to the formulation.

23. A nanocapsule comprising a shell and a core, wherein the core comprises a phase change material configured to absorb heat from hair, scalp, skin, and / or an environment adjacent to the hair, scalp, and / or skin, wherein the phase change material comprises at least two fatty acids.

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